Roll-in shower

I'm contemplating having a roll-in-shower installed in my new house. The bathroom is too small but there is room to enlarge it. Does anyone know how much space is needed?
An idea of cost? Any other aspects of this should I be particularly concerned with? We just closed on the house and I need to have this completed before we move in.

Look for a plumber who has experience doing accessible bathrooms. This is an area where improper waterproofing techniques will hurt you very badly. I would also suggest posting at this excellent tile forum:www.johnbridge.com They are experts in this type of construction.

I'll dig up the links i have describing roll-in showers, on another computer. The main planning concern is with the turning radius for a wheelchair. The main construction challenge is to plan for a drainage slope.